This invention relates to electrical connector systems having mating portions which are brought together to provide a plurality of interengaging electrical contacts. Such systems are used to facilitate connection and disconnection of electronic components. They commonly are designed to be used in conjunction with a "box-and-tray" arrangement, or "racking" system, in which a modular electronic control or communication unit enclosed in a suitable container is mounted on, and supported by, a shelf, or rack, which is secured in place in the environment into which the modular electronic unit is to be inserted. For example, modern aircraft are supplied with such trays, which are normally retained in position on the aircraft, and which are adapted to receive and support boxes containing modular electronic units, such as radio communication units, aircraft instrumentation and component control units, etc. Such modular units are sometimes referred to as "line removal units", or "LRU's". When servicing is required, a given box is removed from the tray and replaced by another. The connection and disconnection of the box, in order to be quickly and efficiently accomplished, requires mating electrical connector sections, one mounted on the tray and wired to the permanent aircraft electrical and electronic systems, and the other mounted on the box and wired to the electrical and electronic systems contained in the box. Each mating connector section carries a number of electrical terminals adapted to engage corresponding electrical terminals on the other.
As is indicated by the prior art patents identified in our related copending application Ser. No. 535,288, numerous efforts have been made to deal with the problem of excessive force needed to bring conventional connector mating sections into engagement, a problem which has grown exponentially as the number of interengaging terminals has proliferated due to the expanding requirements of modern, increasingly sophisticated electronic equipment. As the number of electric terminals in a connector unit increases, there is a serious buildup of all of the forces due to the friction and resilient pressure required in each set of interengaging terminals to insure good contact. As pointed out in a pamphlet titled "Finding the Gremlins in Aircraft Electronic Systems", authored by one of the co-inventors of this application, engaging forces and tolerance buildup resistances related to connector mating problems can result in failure of terminals to establish proper contact and in damaged connectors. This is a significant cause of aircraft functional difficulties.
A proposed solution to this problem is low, or zero, insertion force electrical connectors. In such connectors the contact terminals are not in axial alignment with their corresponding terminals as the two connector mating portions are brought together by relative motion toward one another. Instead, the opposing are laterally spaced until the mating portions have been brought together; and thereafter the set of terminals in one portion is moved laterally, or sideward, into engagement (and therefore electrical contact) with the corresponding terminals in the other portion.
The low insertion force arrangement is designed to minimize the resistance to interengaging movement of the two connector mating sections which otherwise would result from the sum of all the terminal mating forces plus extra resistances caused by any misalignment problems in the connector system.
While low insertion force concepts are very useful in solving the problems experienced with electrical connector systems, we have concluded that the low insertion force solution, of itself, is not sufficient. For one thing, as explained in our related copending application Ser. No. 535,288, we believe an automatic terminal engaging device is necessary to minimize the likelihood of connector functional failure due to human errors. In prior art systems, a separate act by the installer is needed to engage the terminals after the mating portions have been brought together. It is clearly better to minimize the possibility of human errors of omission or comission by making the system as automatic and infallible as possible.
Furthermore, we believe it is necessary to provide connector portions which combine within a single housing, or shell, low insertion force terminals and axially, or telescopically, engaging pin-and-socket terminals in a unitary connector package. We are convinced that low insertion force terminals are not adequate to carry the amperage required by power terminals, and that such terminals cannot be conveniently designed to provide interconnectiion of co-axial conductors which may be needed for high frequency signals. While it has been proposed that such power and co-axial terminals should be "wired around", i.e., electrically connected independently of the low insertion force terminals, the need for a simple, "one-shot", fool-proof method of installing replacement boxes necessitates a unitary connector mating portion which provides the advantages of low insertion force connectors without requiring the time-consuming and errorprone connection and disconnection of separate circuits which cannot be adequately handled by the contacts in low insertion force connectors.